Earlier experiments have shown tht the use of highpass filtering prior to infinite clipping produces a speech signal which is highly immune to noise. Tests were performed to determine the cut-off frequency and asymptotic slope of the highpass filter which yield the highest intelligibility of filtered/clipped speech in noise. Filtered/clipped speech obtained using this optimum filter setting is shown to be considerably more immune to noise than other types of filtered/clipped speech and normal speech heard at the same average power level. Results are shown to confirm earlier views with respect to the significance of the various speech formants.
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